1. Field of the Invention
The present invention relates to a photodetector using a photomultiplier which enables electron multiplications in electron multiplier channels respectively assigned to a plurality of light incidence regions partitioned on an entrance face plate, and a gain control method for the electron multiplier channels in the photomultiplier applied to the photodetector.
2. Related Background of the Invention
U.S. Pat. No. 5,077,504 discloses a photomultiplier having a single entrance face plate partitioned into a plurality of light incidence regions, and having a structure in which a plurality of electron multiplier sections (each constituted by an anode and a dynode unit comprising a plurality of dynode stages) prepared as processing channels (electron multiplier channels) assigned to the plurality of light incidence regions (having a photocathode formed on the inner surface), are sealed inside a single glass tube. A photomultiplier, having such a structure that a plurality of processing channels are contained within a single glass tube, is generally referred to as a “multi-anode photomultiplier,” and as outputs of the respective channels, electrical signals are taken out from the anodes corresponding to the respective channels.